Refractory tiles are used to line the walls of combustion chamber tubes in boilers for incinerating biomass or domestic refuse. The tubes are usually vertical and connected together by cross-bars. The tiles form a refractory lining, protecting the tubes from physical contact with materials during their combustion and with the fumes from that combustion. Thin tiles facilitate heat transfer from the reactor to a fluid flowing in the tubes of the boiler.
Water flows in the tubes to recover part of the heat released during incineration. Close contact between the tiles and the tubes is thus desirable. To this end, as described, for example, in European patent EP-1 032 790, the rear face of each tile conventionally has semi-cylindrical channels shaped so that each receives a tube of the wall of tubes. A thin layer of liquid mortar may also be disposed behind the tiles to limit the volume of the void between the tiles and the tubes, and thus improve heat exchange.
Using floating tiles hung on the wall provides the tiles with a certain degree of mobility relative to one another. To this end, the tiles may, for example, be freely hung on hooks fixed to the middles of bars, and the tiles may be spaced from each other by a few millimeters. The protective lining can thus adapt itself to dimensional variations in the tiles during thermal cycles. The reliability of the lining is thus improved.
The expansion space between two adjacent tiles is generally filled with a flexible mortar to guarantee a seal for the lining. Flexible mortar expansion joints are vulnerable zones and their length must thus be minimized. Conventionally, then, each tile extends over a plurality of tubes. To facilitate positioning of the lining, the dimensions of the tiles must, however, be limited. As an example, the tiles described in EP-1 032 790 extend over three tubes. They include two slots extending either side of a central channel and intended to receive fixing means.
Two types of assembly are possible with the system described in EP-1 032 790.
In a first type of assembly, the hooks are mounted to allow the tiles to be assembled in a pattern that is staggered in the vertical or horizontal direction. Depending on the selected configuration, such an assembly prevents the vertical or horizontal joints from aligning. In practice, that type of assembly proves to be complex and a source of problems. Further, it takes a long time to produce and thus costs are high.
In the second type of assembly, the hooks are disposed in vertical and horizontal lines. However, the configuration of the tiles implies that the spacing of the lines of hooks must vary, which results in an alignment of vertical and horizontal joints. The inventors have found that such an alignment reduces the durability of the joints and thus of the lining.
Further, there are occasional obstacles, for example those formed by passages for thermocouples, which require the assembly to be modified. In particular, it may be necessary to offset one or more rows of hooks, which is an expensive operation. It is also possible to cut one or more tiles. However, cutting inevitably weakens the cut part when in service.
Thus, there is a need for a refractory lining comprising refractory tiles, which lining is easy to use, in particular to accommodate the presence of obstacles, and has improved reliability.
The invention aims to satisfy that need.